bug#42410: Copying nars between stores fails for packages with multiple outputs

[Leo Famulari <leo@famulari.name>]

On Tue, Jul 21, 2020 at 05:49:00PM +0200, Ludovic Courtès wrote:
> Hi,
> 
> Leo Famulari <leo@famulari.name> skribis:
> 
> > Exporting a nar and importing it on another machine only works when the
> > package being built has a single output.
> 
> Note that “guix archive --export foo” only exports foo:out.  If you want
> to export other outputs, you have to explicitly list them.
> 
> > I set up a signing-key on the sending machine, authorized it on the
> > receiving machine, and successfully transferred some nars of
> > single-output packages. I say they succeeded because `guix build
> > --no-grafts foo` did not need to build foo after having imported the nar
> > archive built on the other machine.
> 
> ‘guix build’ starts building unless all the outputs of the package are
> already in the store.
> 
> > However, it fails for packages with multiple outputs such as Syncthing
> > and libsmf.
> 
> Could it be that you copied only one output of the package, and thus
> ‘guix build’ considered it had to build it because the other outputs
> were missing?

Yes, that must be it! Thanks for your reply and I'll re-open this ticket
if necessary.